Indian commuters journey along a major road as heavy smog covers New Delhi on November 7, 2016. (Photo by AFP)

The diesel vehicles of more than 15 years old have been banned in the Indian capital of New Delhi as officials move to enforce fresh measures to contain air pollution.

The office of the lieutenant governor of Delhi, Najeeb Jung, said in a statement that licenses of the vehicles were being withdrawn on Tuesday, leading to the removal of more than 200,000 vehicles from the roads.

Construction work on the underground rail network was also halted in a bid to lift a thick haze of smoke, ash and other pollutants that has blanketed the city of 17 million people. Delhi Metro’s spokesman Anuj Dayal said excavation and back-filling work, which added to the dust levels in the city, had been suspended.

The measures were in line with the rulings of the National Green Tribunal in July that had sought to curb the pollution. The tribunal had ordered the authorities to withdraw licenses of diesel vehicles that were more than 10 years old, although the order fell on deaf ears.

Monday saw the worst levels of air pollution in New Delhi with the US embassy recording levels of PM 2.5 at above 700 in the city’s worst affected areas. The tiny particulate matter reaches deep into the lungs and causes breathlessness, throat irritation and wheezing. The air quality index dropped to 372 by around noon on Tuesday, still in the highest alert “hazardous” zone, which starts at 300.

Environmental groups have criticized government agencies for their delay in implementing the orders of the tribunal. India’s Supreme Court is slated to hear petitions from those groups.

“There is lax action on the court’s directives. There is little recognition of the urgency of toxic air pollution, particularly in the winter months,” said Sunita Narain, the head of the Centre for Science and Environment, adding, “We are asking the court to monitor the implementation of measures.”

Environmentalists have also asked the government to declare the latest outbreak of smog a public health emergency.